need help with this problem, please explain in detail. i appreciate

3. (20 points) The COD (chemical oxygen demand) of a waste has been shown to degrade according to the following rate: r=kC with k having been determined to be 0.1(Lg)0.5min1. If I have a wastewater influent with 1g/L of COD, and treat it in a system consisting of two CSTR's in series of equal volume, each with a mean residence time of 2 hours, what is the expected effluent concentration from the system